MariTide: not an ordinary peptide. What it is and what the research showed

The structure is described in the Phase 1 paper (Nature Metabolism 2024, PMID 38316982):

• One fully human monoclonal antibody that blocks the GIP receptor.
• Two synthetic peptides, analogues of GLP-1, attached to the antibody through a chemical linker. These activate the GLP-1 receptor.
• The total molecular weight is about 153,500 Da, a multiple of a typical peptide's.

In Phase 1 the half-life was about 14 to 16 days for the intact molecule, much longer than that of typical peptides. Administration is subcutaneous, once a month or less often.

The Phase 3 programme is called MARITIME.

• MARITIME-1 (NCT06858839): Focus: Obesity, without diabetes, 72 weeks · Participants: 3,853 · Status (14 Oct 2026): Ongoing
• MARITIME-2 (NCT06858878): Focus: Obesity with type 2 diabetes, 72 weeks · Participants: 1,105 · Status (14 Oct 2026): Ongoing
• MARITIME-CV (NCT07037433): Focus: Cardiovascular disease · Participants: about 12,800 · Status (14 Oct 2026): Recruiting
• MARITIME-HF (NCT07037459): Focus: Heart failure · Participants: about 5,056 · Status (14 Oct 2026): Recruiting
• Two sleep apnoea trials (NCT07225686, NCT07226765): Focus: Sleep apnoea · Participants: about 250 each · Status (14 Oct 2026): Ongoing

For MARITIME-1 and -2 the registry lists 21 January 2027 as the estimated primary completion. This is a registry estimate, not an announced results date.

Phase 2, 52 weeks — peer-reviewed (New England Journal of Medicine 2025, PMID 40549887). Among 592 participants, dosed every 4 or 8 weeks, mean body-weight change was:

• Obesity, 465 people: With drug: −12.3% to −16.2% · Placebo: −2.5%
• Obesity and type 2 diabetes, 127 people: With drug: −8.4% to −12.3% · Placebo: −1.7%

In patients with diabetes, glycated haemoglobin fell by 1.2 to 1.6 percentage points. These values use the paper's treatment-policy estimator.

A note on the numbers: the company also reports larger percentages using a different statistical approach (company announcement). The two approaches must not be mixed. Here we give the figures from the paper.

Phase 1 — peer-reviewed (Nature Metabolism 2024, PMID 38316982). Very small groups, about 8 people per arm. At 420 mg every 4 weeks, mean weight reduction was 14.5% at day 85, versus a 1.5% increase on placebo. Of the 8 participants at that dose, only 4 completed all three doses.

Clinical-trial facts, not usage instructions. MariTide is an investigational compound without approval. All doses are subcutaneous.

• Phase 1, single doses: 21 to 840 mg.
• Phase 1, repeated doses: 140, 280 and 420 mg every 4 weeks.
• Phase 2, obesity: 140, 280 or 420 mg every 4 weeks without step-up. 420 mg every 8 weeks. 420 mg every 4 weeks with a 4-week or 12-week step-up.
• Phase 3: start at 21 mg, then 35 mg, then 70 mg over about 8 weeks, then one of three target doses (Amgen announcement, 23 Jun 2025). The target doses have not been disclosed. The registry (NCT06858839) says only "low, medium, high".

Gastrointestinal events (nausea, vomiting) were the most common. The Phase 2 paper states they were less frequent with step-up dosing and a lower starting dose, and that no unexpected safety signals emerged.

In Phase 1, 68% of those who received at least two doses had gastrointestinal events after the first dose, and only 9% after later doses. Events began 8 to 12 hours after a dose and lasted about 72 hours. No serious events were reported. Four of the eight at 420 mg left before the second dose because of mild gastrointestinal symptoms.

MARITIME-1 excluded people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2, a history of pancreatitis, a past suicide attempt, and diabetes.

• Bone density. It is not reported in the published data we checked, so we draw no conclusion either way.
• Adverse-event rates per dose in Phase 2. They are not included in the paper's abstract.
• The Phase 3 target doses.
• Phase 3 results. None exist yet.

This content is educational and research-oriented. MariTide is an investigational compound, is not approved as a medicine, and is not intended for human use. This is not medical advice.